We quantified the availability of breeding habitat of the endangered Hawaii Akepa (Loxops coccineus). The species is thought to nest excusively in natural cavities within mature ohia (Metrosideros polymorpha) trees but birds commonly occur in short stature trees that presumably do not have any natural cavities because of their polyploidal (many-branched) structure. To test this hypothesis we searched for cavities in trees where akepa forage and we measured diameter of each stem of each tree examined. The habitat is in montane areas of Hawaii Volcanoes National Park on Mauna Loa volcano.We surveyed 57 plots, 49 in montane woodland and 8 in closed-canopy forest. Six tree cavities were detected in the 214 sampled trees: five cavities were found in 38 trees sampled in closed canopy forest (8.9/ha) and only one cavity was found in 176 trees sampled in montane woodland (0.29/ha). Tree diameters in the forest ranged from 10 cm to 128 cm diameter at breast height (DBH), while those in the woodland were much smaller ranging from 10 cm to a maximum DBH of 54 cm. Most trees in the closed-canopy forest were monopodial (87%, mean number of stems per tree = 1.16, SE = 0.07) with only five of the 38 trees having multiple stems at DBH height. In contrast, most trees in the woodland were sympodial (61%, mean number of stems per tree = 2.11, SE = 0.11) where 108 of the 176 trees had multiple stems. This data release includes two CSV files: the ohia measurements and locations.